DE3211047C2 - - Google Patents

Description

The invention relates to a sintered hard metal body Tungsten carbide as the main component and cobalt, nickel, iron or their alloys as binders and, if necessary, with a hard, dense, high-melting, firmly adhering coating.

The invention further relates to a method of manufacture of such a hard metal body by producing a powder mixture desired composition, pressing this Mixture, sintering the compact and optionally applying a high melting coating.

So far, the surfaces of carbide cutting inserts with various hard, high-melting Coatings added to the durability of the cutting edge improve and thereby the lifetime of the assignment, d. H. the time during which the use for cutting can actually be used to extend (cf. for example US Pat. Nos. 40 35 541, 35 64 683, 36 16 506, 38 82 581, 39 14 473, 37 36 107, 39 67 035, 39 55 038, 38 36 392 and the U.S. reissue patent 29 420. These well-known high-melting coatings can  but unfortunately the toughness of the cemented Reduce carbide inserts to different degrees. The The extent of the drop in quality depends at least in part on the Structure and composition of the coating and process used for his departure. Although high-melting coatings have the durability of Metal cutting inserts have improved, they have not the susceptibility of the cutting edge to damage reduced by flaking or breaking, especially in the case of Applications where cutting is intermittent is carried out.

The previous efforts to improve toughness or the edge strength of coated, with Covered cutting inserts always circled the production of a layer enriched with cobalt, which is different from the interface between the substrate and the coating extends inwards. It was found that a cobalt accumulation in the surface layers in certain substrates with a type C porosity when cycling through vacuum sintering processes is achieved. These zones enriched with cobalt were characterized by type A porosity, while the bulk of the substrate is predominantly one Type C porosity. Usually was in the with Cobalt-enriched zones impoverished on solid Carbide solution to different depths and in different Extent. The cobalt enrichment is desirable because we know that increasing the cobalt content the toughness or impact resistance of hard metals elevated. Unfortunately, it is difficult Extent of enrichment achieved in substrates with a To control type C porosity. For example, a Coating of cobalt and carbon on the surface of the substrate formed. This cobalt and Carbon was deposited before the high melting point Material removed on the substrate to make it adherent  To achieve connection between the coating and the substrate. Occasionally, the level of cobalt accumulation in the layers below the surface of the Substrate so high that just opposite, adverse effects on the durability of the side Boundary areas (flanks) resulted. As a result from this, the layer enriched with cobalt was exposed the lateral boundary surfaces of the substrate sometimes ground away, so that the cobalt enrichment only on left the cutting breasts. Compared to substrates with a porosity of type A or B are substrates with a porosity of type C chemically not so homogeneous. From this can the formation of eta phase (a hard and brittle phase, which affects toughness) at the interface between coating and substrate are poorly controlled and there is a reduction in Adhesion of the coating and an increase in the uneven Result in coating growth.

By definition, the porosity of cemented carbides after three from the ASTM (American Society for Testing and Materials) recommended categories as follows:

• Type A for pore sizes with diameters of less than 10 µm;
• Type B for pore sizes with diameters between 10 and 40 µm;
• Type C for irregular pores caused by the presence are caused by carbon inclusions. These inclusions are made during the metallographic Production pulled out of the sample, being said irregular pores stay behind.

The porosity observed can be in addition to the above Classification of a number between 1 and 6 assigned to the extent or frequency of make the porosity identified. The method, according to which this classification is carried out is described in: Dr. P. Schwarzkopf and Dr. R. Kieffer, Cemented Carbides, McMillan Co., New York, pp. 116-120 (1960).

Sintered hard metals can also add up to their contents Carbon and tungsten binders are classified. Tungsten carbide-cobalt alloys with an excess of Carbon is characterized by type C porosity, which, as already mentioned, by inclusions of free Carbon is formed. Tungsten carbide-cobalt alloys with low carbon, where the cobalt saturated with tungsten are characterized by the Presence of eta phase, an M₁₂C- or M₆C- Carbide, wherein M represents cobalt and tungsten. Between the extremes of porosity of type C and eta phase there is a range of intermediate compositions from bonding alloys that contain tungsten and carbon contained in different amounts in solution, whereby however neither free carbon nor eta phase is present are. The tungsten content in tungsten carbide-cobalt alloys can also be caused by the magnetic saturation of the binding alloy are marked as the magnetic Saturation of the cobalt alloy is a function of its composition is. According to literature, carbon saturated Cobalt has a magnetic saturation of 158 Gauss · cm³ / g Cobalt and indicates a type C porosity, while a magnetic saturation of 125 Gauss · cm³ / g Cobalt and below on the presence of eta phase indicates.

From Kieffer / Benesovsky, hard metals, Springer-Verlag 1965, Pages 19, 76, 88, 89 and 99 to 105 are cemented carbides and methods for their preparation are known. In doing so  especially the systems W-Co-C, WC-TiC-Co, TaC (NbC) -Co and WC-TiC-TaC (NbC) -Co, partly based on phase diagrams, described in detail, including the operations be examined during sintering. So z. B. found (Page 88) that thin cobalt-containing intermediate layers already during the grinding process of the raw materials by diffusing the cobalt into the surface of the Tungsten carbide grains are created that are magnetically detectable are. On the other hand (page 89) it was found that in the double sintering process in the temperature range between 600 and 1250 ° C parallel to the solidification of the cobalt one Solution of free carbon and the finest toilet particles takes place in cobalt. As a binder for hard carbides cobalt, nickel and iron (page 105) are discussed.

From the magazine VDI-Z 122 (1980), No. 13, pages 155 to 159, are coated hard metals and their use as Known cutting materials, the hard metals from the systems WC-Co, WC-TiC-TaC-Co and StiC-Mo-Ni are constructed and optionally a 3 to 12 µm thick, binder-metal-free coating may have several hard material layers. As hard materials for the coating, TiC, TiN, Ti (C, N) and / or Al₂O₃ can be used.

Despite the large number of known sintered carbide bodies and processes for their manufacture still a need for usable as cutting inserts, sintered carbide bodies with improved toughness and edge strength as well as a process their manufacture. The invention is based on the object to satisfy this need.

This object is achieved by the sintered Hard metal body according to claim 1 and that Method according to claim 10.  

Advantageous embodiments of the hard metal body according to the invention are characterized by the features of the claims 2 to 9, advantageous embodiments of the invention Process by the features of the claims 11 and 12 marked.

It has been found that when the process according to the invention is carried out, the addition is converted at least partially by absorption of carbon from the tungsten carbide into the corresponding carbide and that a layer ( 14 ) enriched with binder is formed near the outer surface of the sintered hard metal body, which is preferably over its entire cross-section has a porosity that is essentially only of type A or B. Enrichment can also be accomplished in hard metal bodies with carbon contents ranging from the eta phase to Type C porosity.

The hard metal bodies according to the invention also have a layer ( 16 ) below said layer ( 14 ) enriched with binder, which layer is partially depleted of binder.

Cobalt is preferably used as the binder.

The hard metal bodies according to the invention have a layer ( 14 ) near their outer surface which is depleted of carbide in solid solution, and they also have a further layer ( 14 ) below the depleted layer ( 14 ) in the form of a solid solution. 16 ), which is enriched with carbides present in solid solution.

The hard metal bodies according to the invention have preferably a cutting edge at the meeting point a cutting breast with a side Boundary surface with a hard, dense, high melting coating that adheres with is connected to these areas. The one enriched with binder Layer can be from the side boundary surface sanded before coating with the coating will.

The high-melting coating preferably consists of one or more layers of metal oxide, carbide, nitride, boride or carbonitride.

The invention is based on the Drawing explained further. It is

Fig. 1 is a schematic cross-section through an embodiment according to the invention of a coated, useful as a metal cutting insert cemented carbide body

Fig. 2 is a graph of characteristic cobalt enrichment levels, which have been generated in an inventive cemented carbide body as a function of distance (depth) of their rake faces,

Fig. 3 is a graph showing the change of the relative concentrations of the binder and in the form of solid solution carbides present in dependence on the distance (depth) of the rake faces of a sample prepared according to Example 12.

The above objects of the invention are achieved by Heat treatment of a compact that contains an element that contains a carbide with a more negative one free formation energy than tungsten carbide with increased Temperature forms which is close to or above the melting point lies. This element will from the group of IV B and V B transition metals (Ti, Zr, Hf, V, Nb, Ta) selected and from their alloys, Nitrides, carbonitrides and hydrides. It was found, that the edge of a cemented tungsten carbide body immediately adjacent material layer throughout can be enriched with binder and usually at least in part in the form of a solid solution Carbide can be depleted, during sintering or reheating to a temperature, those above the melting point of the binding alloy lies, by adding additives of nitrides, hydrides and / or carbonitrides of the elements of groups IV B and V B of the periodic system in the powder feed.

These additives of groups IV B react during sintering and V B with carbon to form carbides or Carbonitrides. These carbides or carbonitrides can in whole or in part in the form of a solid solution Tungsten carbide and others, if any Carbides are present. The one in the finished sintered carbide present nitrogen content is compared to that in the form a nitride or carbonitride added nitrogen content characteristically diminished because of these additives at elevated temperatures above and below the Melting point of the binding alloy are unstable and at least partial volatilization of Take nitrogen out of the sample when the sintering atmosphere contains a lower nitrogen concentration than yours Equilibrium vapor pressure corresponds. If the addition in the form of metal, alloy or Hydride is added, it also becomes cubic  Carbide converted that characteristically together with tungsten carbide and possibly others present Carbides are in the form of a solid solution. The hydrogen evaporated from any added hydride during sintering.

The metals tantalum, titanium, niobium and hafnium and their Hydrides, nitrides and carbonitrides can be used alone or in Combination can be used to create a continuous Promote cobalt enrichment through Sintering or subsequent heat treatment of alloys based on tungsten carbide cobalt with an inside carbon limits. It was found that additives totaling up to about 15% by weight are usable. The metals are believed to be zirconium and vanadium and their nitrides, carbonitrides and hydrides are also suitable for this purpose. In alloys with a porosity of type A and B and in carbon deficiency Alloys containing eta phase are made cobalt enrichment without the formation of an external one Cobalt or carbon top layer, so that on this Way the need is avoided, a surplus of cobalt and carbon from the cemented carbide surfaces to remove before the high-melting Coating is applied.

Additions of about 0.5 to 2% by weight, in particular Additions of titanium in the form of titanium nitride or titanium carbonitride for alloys based on tungsten carbide Cobalt are preferred. Because titanium nitride during vacuum sintering does not remain completely stable, which makes the nitrogen is at least partially evaporated preferably half a mole of carbon per mole of added nitrogen added to the for a Tungsten-lean cobalt binding alloy necessary Maintain carbon content. It was found, that the cobalt enrichment by way of heat treatment of alloys based on tungsten carbide-cobalt  runs more easily if the alloy is leaned to W. Contains W-Co-Binder. The lean tungsten cobalt binder should preferably be used a magnetic saturation of 145 to 157 Gauss · cm³ / g Have cobalt. Additions of titanium nitride along with the necessary carbon additives to powder mixtures based on tungsten carbide cobalt accelerate the Formation of cobalt binding alloy with a magnetic Saturation from 145 to 157, which is usually only is difficult to reach. Although a cobalt binding alloy with a magnetic saturation of 145 to Alloys can also be preferred to 157 Gauss · cm³ / g cobalt enriched, the tungsten-cobalt binding alloys contain, which are saturated with tungsten (less than 125 gauss · cm³ / g cobalt).

A cobalt enrichment layer was found with a layer thickness of more than 6 µm to a clear one Improve the edge strength of with high-melting Coated carbide inserts leads. Although cobalt enrichments up to one A depth of 125 µm has been achieved with cobalt Enriched layer with a thickness of 12 to 50 µm for the application of the coated cutting inserts prefers. The cobalt content is preferably the same as Cobalt-enriched layer on one with a high-melting Covered insert between 150 and 300% of the average cobalt content, measured on the surface using X-ray structure analysis.

It is believed that binder enrichment occurs in all tungsten carbide binder cubic carbide (ie, tantalum, niobium, titanium, vanadium, hafnium, zirconium) alloys that do not sinter together into a continuous carbide backbone. These alloys, which contain 3% by weight or more of binder, accumulate with layer 14 when the method according to the invention is used. When applying the invention to cutting inserts, however, a binder content of between 5 and 10% by weight of cobalt and a total content of cubic carbide of 20% by weight or less is preferred. Although cobalt is the preferred binder, nickel, iron, and nickel-iron alloys and alloys of nickel and iron with cobalt can also be used instead. Other binding alloys containing nickel, cobalt or iron can also be used.

The ones used to achieve binder enrichment Sintering and heat treatment temperatures are the ones for that Liquid sintering characteristic temperatures. For These temperatures are based on cobalt-based alloys 1285 to 1540 ° C. The sintering runs should at least Take 15 minutes at the sintering temperature. The results can be further optimized by using controlled Cooling speeds, from heat treatment temperatures down to a temperature below the melting point of the binding alloy. These cooling rates should be between 25 and 85 ° C / h, preferably between 40 and 70 ° C / h. The procedural stage heat treatment for cutting inserts with one Cobalt binder takes 30 to 150 particularly advantageously Minutes at 1370 to 1500 ° C, followed by cooling to 1200 ° C at a speed of 40 to 70 ° C / h. The pressure applied during the heat treatment can vary from 0.133 Pa up to those elevated Pressures that are common in hot isostatic pressing be applied. The preferred pressure is between 0.133 and 0.200 hPa. If nitride or carbonitride Additives are used, the vapor pressure of the nitrogen in the sintering atmosphere, preferably below its equilibrium pressure to prevent the volatilization of the Allow nitrogen from the substrate.

Since the first enrichment takes place during sintering, can grind stages in the manufacturing process the metal cutting inserts the enriched zones again  remove. In such cases, subsequent heat treatment can be used according to the parameters above Development of a new enriched layer below of the outer surfaces.

Binder-enriched substrates for coated Cutting inserts can have binder enrichments on both Have sides, both on the cutting breasts as well on the flanks. However, depending on the type of use the binder enrichment on the flanks also removed be, but this is not necessary to achieve an optimal Achieve functioning in all cases.

The binder-enriched substrates can be used the coating techniques known to those skilled in the art coated to produce high-melting coatings will. Although the applied high-melting coating can have one or more layers which consist of the Group IV B and V B of the periodic system selected Materials such as carbides, nitrides, borides and carbonitrides as well as oxide or oxynitride of aluminum, so it was found that a combination of good Cutting edge strength and edge durability achieved can be achieved by combining a substrate with a layer enriched with binder according to the invention a coating of:

• - Alumina over an inner layer Titanium carbide;
• or an inner layer of titanium carbide, bonded to an intermediate layer of titanium carbonitride, that to an outer layer Titanium nitride is bound;
• or titanium nitride bound to an inner one Layer of titanium carbide.

A hard metal body is particularly preferred with a binder-enriched invention Layer in connection with a titanium carbide / aluminum oxide  Coating. In this case the coating should be an overall thickness from 5 to 8 µm.

In Fig. 1, an embodiment for a coated hard metal body according to the invention in the form of a metal cutting insert 2 is shown schematically. The insert 2 comprises a substrate in the form of a hard metal body 12 with a layer 14 enriched with binder and a layer 16 depleted in binder over the main part 18 of the substrate 12 , the chemical properties of which essentially correspond to the chemical properties of the original powder mixture.

A layer 14 enriched with binder is located on the cutting breasts 4 of the hard metal body 12 , the layer 14 having been ground down on the lateral boundary surfaces, the flanks 6 , of the body. Below the layer 14 enriched with binder, that is to say in the direction of the interior of the body 12 , in the exemplary embodiment shown there is a zone 16 depleted of binder. It has been found that this zone 16 depleted in binder develops together with the layer 14 enriched in binder when hard metal bodies are produced by the method according to the invention.

Binder-depleted zone 16 is partially depleted of binder while being enriched with solid solution carbides. The enriched layer 14 is partially depleted of carbides present in solid solution. The substrate material of the main part 18 is located below the zone 16 depleted of binder.

A cutting edge 8 is formed at the point where the cutting breasts 4 and the flanks 6 meet. Although the cutting edge 8 shown here is honed, honing the cutting edge is not necessary for all applications of the present invention. From Fig. 1 it can be seen that the layer 14 enriched with binder extends into this cutting edge zone and preferably adjoins the majority of the honed cutting edge 8 , if not the entire cutting edge 8 . The zone 16 depleted of binder extends to the surface of the flank 6 , just below the cutting edges 8 . A high-melting coating 10 is bonded to the outer surface of the hard metal body 12 .

These and other features of the invention will become apparent from the following examples explained in detail:

Example 1

A mixture containing 7000 g of powder was run for 16 hours long with a paraffin, a surfactant, a solvent and with cobalt-bonded tungsten carbide Cycloids ground and mixed, in following quantities and ratios:

There were rectangular insert blanks with dimensions from 15.1 x 15.1 x 5.8 to 6.1 mm and with a weight of 11.6 g under a force of 8200 kg to tablets pressed. These inserts were at 1496 ° C for 30 minutes long vacuum sintered and then among those in the furnace Conditions cooled. After sintering, they weighed  Inserts 11.25 g and were 13.26 × in size 13.26 x 4.95 mm. These missions were then completed of SNG433 standard dimensions processed as follows (This identification number is on the labeling system supported by American Standards Association was developed and developed by the Cutting tool industry was generally taken over. The international marking is: SNGN 12 04 12):

• 1. The upper and lower surfaces (cutting breasts) the inserts were made to a thickness of 4.75 mm ground.
• 2. The inserts were placed under one for 60 minutes 100 micron vacuum heat treated at 1427 ° C and then at a rate of 56 ° C / h Cooled 1204 ° C and then under the surrounding Oven conditions cooled.
• 3. The lateral boundary surfaces (flanks) were up to a square with a side length of 12.70 mm ground, and the cutting edges were honed to a radius of 0.064 mm.

A titanium carbide / titanium carbonitride / titanium nitride coating was then applied to the ground inserts, using the following chemical vapor deposition method (CVD) in the order listed below of the individual steps:  

Table I

Along with the above bets, bets became bets made from the same powder mixture, but without Made of TiN and its accompanying carbon additive were. The coated coatings showed the following microstructural Dates on:

Example 2

Green, tablet-shaped inserts were made accordingly Example 1 and using that in Example 1 described mixtures with and without TiN and its accompanying Carbon additives made. These stakes were at 1496 ° C for 30 minutes under a vacuum of 25 microns sintered and then under the conditions prevailing in the furnace cooled down. They were honed (0.064 mm radius) and then CVD coated with TiC / TiCN / TiN, accordingly the method shown in Table I. It is note that in this example, the one enriched with cobalt Layer on both the flanks and on top the cutting breasts.

The coated inserts were carefully evaluated, whereby the following results were obtained:

Example 3

A mixture of the following materials was used along with a surfactant, a volatile binder, a solvent and 114 kg of cycloids in one cylindrical mill brought:

The powder feed was adjusted so that in the Feed total carbon content 6.25% by weight revealed. The feed was mixed for 90 261 revolutions and grind, with an average particle size of 0.90 µm. The mixture then became moist sieved, dried and placed in a hammer mill. Moldings were made and then added for 30 minutes Sintered at 1454 ° C and then under furnace ambient conditions chilled.

This treatment resulted in a sintered blank a magnetic saturation of 117 to 121 in total Gauss · cm³ / g cobalt (including the body and the material enriched with binder). The microstructural Evaluation of the sintered blank showed: eta phase present through the entire blank; Porosity of types A-2 to B-3; Thickness of those enriched with cobalt Zone about 26.9 µm; Thickness of solid solution depleted zone about 31.4 µm.  

Example 4

The following materials were made into one with a Grinding container lined with tungsten carbide-cobalt alloy with an inner diameter of 190 mm and a length given by 194 mm. In addition, in the grinding bowl 17.3 kg of 3.2 mm tungsten carbide-cobalt cycloids given. These materials were made by rotating the grinding bowl around its cylinder axis with 85 revolutions per Minute for 72 hours (that's 367 200 revolutions) ground and mixed together.

Feed composition

283 g (4.1% by weight) TaC 205 g (3.0% by weight) NbC 105 g (1.5% by weight) TiN 7.91 g (0.1% by weight) C 381 g (5.5% by weight) Co 5946 g (85.8% by weight) WC 105 g paraffin (Sunoco 3420)
14 g surfactant (Ethomeen S-15)
2500 ml perchlorethylene

This mixture was weighed out so that a 2 wt .-% Binding alloy containing tungsten-98% by weight cobalt arises. After grinding and mixing, the mixture became wet sieved to oversize particles and contaminants to remove, then was at 93 ° C under a nitrogen atmosphere dried and in a hammer mill ground to agglomerates to break up.

With this powder, compacts were made and then sintered at 1454 ° C for 30 minutes and under ambient conditions chilled.

The top and bottom surfaces, i.e. H. the cutting breasts, des The insert was then ground until the final thickness was reached. This was followed by heat treatment  1427 ° C under a vacuum of 100 microns. After 60 minutes at this temperature the inserts were at a rate cooled from 56 ° C / h to 1204 ° C and then cooled in the oven under the ambient conditions there. The side surfaces (flanks) were then ground so that there is a square of 12.70 mm side length revealed, and the cutting edges of the insert were honed to a radius of 0.064 mm. This treatment resulted in an insert substrate in which only the cutting breasts a solution enriched with cobalt and poor in solid solution Zone had, these zones from the side Boundary surfaces (flanks) were ground away.

The inserts were then placed in a coating reactor inserted and coated with a thin layer of titanium carbide, using the following chemical Vapor deposition method. The hot one, containing the stakes Zone was first heated from room temperature to 900 ° C. Hydrogen gas was released during the heating through the reactor at a rate of 11.55 l / min flow through. The pressure in the reactor was on something held less than one atmosphere. The hot zone was then heated from 900 ° C to 982 ° C. During this second heating the reactor pressure was at 180 torr kept, a mixture of titanium tetrachloride and Hydrogen as well as pure hydrogen gas in the reactor with a flow rate of 15 l / min or 33 l / min occurred. The mixtures of titanium tetrachloride and Hydrogen gas was obtained by using the hydrogen gas flowed through an evaporator that did that Titanium tetrachloride kept at a temperature of 47 ° C. After reaching 982 ° C, methane was let into the reactor Flow in at a speed of 2.5 l / min. The Pressure in the reactor was reduced to 140 torr. Under these The titanium tetrachloride reacts with methane in conditions Presence of hydrogen to titanium carbide on the hot Surface of the insert. These conditions were Maintained for 75 minutes, after which the inflow of  Titanium tetrachloride, hydrogen and methane prevented has been. The reactor was then allowed to cool, taking argon through the reactor at a flow rate of 1.53 l / min under slightly less than one atmosphere of pressure streamed.

The examination of the microstructure of the finished insert showed a zone enriched with cobalt that extends up to 22.9 µm into the interior and a zone the cubic in the form of a solid solution Carbide was depleted and up to 19.7 µm from the Cutting breasts of the substrate extended into the interior. The porosity in the enriched zone and the remaining part of the substrate was between A-1 and A-2 estimated.

Example 5

In this example the material was used a two-stage grinding process with the following feed mixed and ground:

Stage I (489 600 revolutions)

141.6 g (2.0% by weight) TaH 136.4 g (1.9% by weight) TiN 220.9 g (3.1% by weight) NbC 134.3 g (1.9 Wt%) TaC 422.6 g (5.9 wt%) Co 31.2 g (0.4 wt%) C 14 g surfactant (Ethomeen S-15)
1500 ml perchlorethylene

Stage II (81 600 revolutions)

6098 g (84.9% by weight) WC 140 g paraffin (Sunoco 3420)
1000 ml perchlorethylene

This composition was chosen so that a binding alloy from 2 wt .-% W and 98 wt .-% Co arose.  

The test inserts were then made and with TiC coated accordingly, as described in Example 4 Trial blanks.

The microstructural examination of the coated inserts resulted in porosity of A-1 both in that with cobalt enriched material as well as in the material of the main part. The zone enriched with cobalt and the solid solution zone impoverished zone extended from the cutting breasts in the inside to a depth of about 32.1 or 36 µm.

Example 6

The following materials were placed in a grinding jar 190 mm inner diameter spent:

283 g (4.1% by weight) TaC 205 g (3.0% by weight) NbC 105 g (1.5% by weight) TiN 7.91 g (0.1% by weight) C 381 g (5.5% by weight) Co 5946 g (85.8% by weight) WC 140 g paraffin (Sunoco 3420)
14 g surfactant (Ethomeen S-15)
2500 ml perchlorethylene

This mixture was balanced so that there was a binding alloy with 2 wt .-% W and 98 wt .-% Co resulted.

Cycloids were also added to the mill. The The mixture was then ground for four days. The mixture was in a Sigma mixing pump at 121 ° C under a Partial vacuum dried, after which it goes through in the hammer mill a 40 mesh sieve was classified.

SNG433 inserts were then made using the method described in Example 4 method described. The stakes According to this example, however, a TiC / TiN CVD coated. The following coating process was used used:  

1. TiC coating

The patterns in the coating reactor were under one Vacuum of 125 torr maintained at about 1026 to 1036 ° C. Hydrogen carrier gas flowed into a TiCl₄ evaporator at a speed of 44.73 l / min. The evaporator was under vacuum at a temperature of 33 to 35 ° C held. TiCl₄ vapor was carried away by the H₂ carrier gas and dragged into the coating reactor. Free hydrogen and free methane flowed into the coating reactor at 19.88 and 3.98 l / min. These conditions were Maintained for 100 minutes and resulted in one dense TiC coating that was firmly adhered to the substrate.

2. TiN coating

The stream of methane flowing into the reactor was interrupted and replaced by N₂, the nitrogen with flowed into the reactor at a rate of 2.98 l / min. These conditions were maintained for 30 minutes and resulted in a dense TiN coating that adhered was bound to the TiC coating.

The evaluation of the coated inserts showed the following Values:

Porosity A-1, through and through thickness of the zone enriched with cobalt17.0 to 37.9 µm thickness of the zone depleted in solid solution up to 32.7 µm thickness of the TiC / substrate intermediate layer, eta phase up to 3.9 µm thickness of the Coating
TiC3.9 µm TiN2.6 µm Mean Rockwell "A" hardness of the body 91.0 coercive force, Hc98 Oersted

Example 7

Using the following two step milling process a mixture of materials was produced:

In stage I, the following materials were used along with 17.3 kg of 4.8 mm toilet co-cycloids in a grinding container with 181 mm inner diameter and 194 mm length, who was lined with toilet co. the grinding bowl was around its cylinder axis at 85 revolutions per minute Rotates for 48 hours (244,800 revolutions).

140.8 g (2.0% by weight) Ta 72.9 g (1.0% by weight) TiH 23.52 g (0.3% by weight) C 458.0 g (6.5 Wt%) Co 30 g surfactant (Ethomeen S-15)
120 g paraffin (Sunoco 3420)
1000 ml solvent (Soltrol 130)

In stage II 6314 g (90.2 wt .-%) WC and 1500 ml Soltrol 130 added and the whole feed additionally Rotates for 16 hours (81,600 revolutions). This Mixture was balanced so that there was a binding alloy with 5 wt .-% W and 95 wt .-% Co resulted. After grinding the mixture was sieved wet through 400 mesh, under Nitrogen dried at 93 ° C for 24 hours and placed in a Hammer mill brought with a 40 mesh sieve.

Test pieces were uniaxial with a total force of 16,400 kg to a size of 15.11 x 15.11 x 5.28 mm (8.6 g / cm³ specific weight) pressed.

The green test pieces described above were at 1468 ° C for 150 minutes under a vacuum of one Micron sintered. The bets were then placed under them ambient furnace conditions cooled. As a release agent between the test inserts and the graphite sinter boxes flake graphite was used.  

The inserts sintered in this way were placed on one Honed radius of 0.064 mm. The stakes were then with a TiC / TiCN / TiN coating according to the following procedure coated:

• 1. Inserts were placed in the reactor, and the Air was flowing out of the reactor with the help Driven out of hydrogen.
• 2. The inserts were heated to about 1038 ° C where the flow of hydrogen through the reactor was maintained. The pressure in the coating reactor was on slightly more than one Atmosphere.
• 3. TiC coating:
  A mixture of H₂ + TiCl₄ entered the reactor for 25 minutes at a rate of about 92 l / min and methane at a rate of 3.1 l / min. The TiCl₄ evaporator was kept at about 6 psi and 30 ° C.
• 4. TiCN coating:
  The flow of the H₂ + TiCl₄ mixture was maintained for 13 minutes; the methane flow was reduced by half; N₂ was introduced into the reactor at a rate of 7.13 l / min.
• 5. TiN coating:
  The methane flow was interrupted for 12 minutes and the nitrogen flow rate was doubled. With the completion of the TiN coating, both the flow of the H₂ + TiCl₄ mixture and the N₂ flow were interrupted, the heating elements of the reactor were switched off and the reactor was blown through with free H₂ until it had cooled to about 250 ° C. The reactor was flushed with nitrogen at 250 ° C.

It was found that the insert substrates were a Porosity of type A-1 to A-2 in their non-enriched Inside, i.e. the material of the main part. One zone enriched with cobalt and one more solid Solution depleted zone extended from the surfaces about 25 µm or 23 µm towards the inside. The non-enriched interior had a medium Rockwell "A" hardness of 91.7. The coercive force, Hc, of the substrate was found to be 186 Oersted.

Example 8

Using the following two-step mixing and milling process 260 kg of a powder mixture with a Carbon content that was balanced so that there is a C3 / C4 porosity revealed:

Level I

The feed composed as follows was 96 hours long grinding:

10 108 gTaC (6.08% carbon) 7321 gNbC (11.28% carbon) 3987 gTiN 1100 gC (Molocco Black - a product of Industrial Carbon Corp.) 16 358 gCo 500 g surfactant (Ethomeen S-15)
364 kg 4.8 mm Co-WC cycloid

Stage II

The following mixes were added to the above mix added and the resulting mixture further Grind for 12 hours:  

221.75 kg WC (6.06% by weight carbon) 5.0 kg paraffin (Sunoco 3420)

The finished mixture was then sieved wet, dried and treated in the hammer mill.

Then insert blanks were pressed and subsequently Sintered at 1454 ° C for 30 minutes. This sintering resulted a zone enriched with cobalt, which contains the main part C3 / C4 porosity. The sintered blanks were then ground and honed until the dimensions of the SNG433 inserts were achieved, the ones with cobalt enriched zone was removed.

The sintered inserts were then placed in an open one Graphite canister packed with flake graphite. This compilation was then at 1371 to 1377 ° C for one hour under an atmosphere of 25 vol .-% N₂ and 75 vol .-% He hot isostatic at a pressure of 8.76 × 10⁷ Pa pressed (HIPed). The microstructural examination of a HIPed pattern revealed that during the hot isostatic Pressing a zone of depth enriched with cobalt 19.7 µm. Also emerged about 4 µ of the cobalt surface and 2 µ of the surface Carbon because of the type C porosity used Substrate.

Example 9

A mixture of the following materials was made in one Ball mill grinding:  

30.0% by weight WC (1.97 µm average particle size) 750 kg 51.4% by weight WC (4.43 µm average particle size) 1286 kg 6.0 wt% Co150 kg 5.0 wt% WC-TiC carbide in solid solution 124.5 kg 6.1% by weight TaWC carbide in solid solution 152 kg 1.5% by weight W37.5 kg

This mixture was composed so that a Total carbon content of 6.00 wt .-% resulted. These Materials were 51 080 revolutions with 3409 kg WC- Cycloids and 798 l paraffin ground. The final particle size was 0.82 µm.

5000 g of the powder was mixed and ground from the Approach separated, and the separated amount the following materials were added:

1.9% by weight of TiN (pre-ground to about 1.4 to 1.7 µm) 96.9 g 0.2 wt% C (Ravin 410) 9.4 g 1500 ml perchlorethylene

These fabrics were then lined with a tungsten carbide Grinding container with an inside diameter of 190 mm with 50 vol.% WC cycloids (17.3 kg) for 16 hours grind. After grinding was completed, the divided one Sifted wet through a 400 mesh screen, under a partial vacuum in a Sigma mixing pump Dried 121 ° C and in a 40-mesh sieve hammer mill given.

SNG433 blanks were pressed with a force of 3600 kg, with a bulk density of 8.24 g / cm³ and a blank height from 5.84 to 6.10 mm.

The blanks were placed on a at 1454 ° C for 30 minutes  NbC powder release agent under a vacuum of 10 to 25 Micron sintered and then cooled in the oven. The sintered Samples had dimensions of 4.93 × 13.31 × 13.31 mm, a density of 13.4 g / cm³ and a total magnetic saturation from 146 to 150 Gauss-cm³ / g Co. The microstructural Evaluation of the sample pieces showed a continuous Type A porosity and one enriched with cobalt Layer about 21 microns thick.

The top and bottom sides (cutting breasts) of the inserts were then ground down to a total thickness of 4.75 mm. The inserts were then at 1427 ° C for 60 minutes heat treated for a long time under a vacuum of 100 microns, cooled to 1204 ° C at a rate of 56 ° C / h and then chilled in the oven.

The flanks of each insert were sized to one Ground with a side length of 12.70 mm and the Edges honed to a radius of 0.064 mm.

The inserts were then covered with titanium carbide / alumina CVD coated using the following method.

The inserts were placed in a coating reactor and heated to about 1026 to 1030 ° C and under one Vacuum maintained from 117 to 166 hPa. Hydrogen gas flowed through at a speed of 44.73 l / min a TiCl₄ containing evaporator at 35 to 38 ° C below Vacuum. TiCl₄ vapor was mixed with the hydrogen in the Coating reactor towed. Streamed at the same time Hydrogen and methane in the reactor at speeds of 19.88 and 2.98 l / min. These conditions (vacuum, Temperature, flow rate) were 180 minutes long, with a firmly adhering TiC coating emerged on the stakes. Then the hydrogen flow to the evaporator and the methane flow into the reactor interrupted. Hydrogen and chlorine were then let in  flow a generator, the aluminum particles at 380 contained up to 400 ° C and 0.5 psi pressure. Hydrogen and Chlorine poured into the generator gate at speeds of 19.88 l / min or 0.8 to 1.0 l / min. The chlorine reacted with the aluminum to AlCl₃ vapors, which are then in the reactor were directed. While hydrogen and AlCl₃ in the Reactor flowed, CO₂ was left at one speed of 0.5 l / min also flow into the reactor. These Flow rates were maintained for 180 minutes meanwhile the inserts at a temperature from 1026 to 1028 ° C under a vacuum of about 88 goal were held. This procedure resulted in one dense coating of Al₂O₃ that adheres to one inner coating made of TiC was bound.

The evaluation of the coated inserts showed the following Values:

Porosity A1 in the enriched zone, A1 with isolated B in the material of the main part Thickness of the zone enriched with cobalt (cutting breast) about 39.3 µm thickness of the zone depleted in solid solution (cutting breast) up to 43.2 µm thickness of the coating
TiC5.9 µm Al₂O₃2.0 µm Mean Rockwell "A" hardness in the main part of the substrate 91.9 coercive force, Hc170 Oersted

Example 10

A further 5000 g of the mixture was removed from the original batch prepared according to Example 9 separated. Pre-ground TiCN in an amount of 95.4 g (1.9% by weight) and 1.98 g (0.02% by weight) of Ravin 410 carbon black was added to this  Mixture added, mixed for 16 hours, sieved, dried, put in the hammer mill, as in Example 9 described.

Test pieces were pressed into tablets, at 1496 ° C Vacuum sintered for 30 minutes and then cooled in the oven, with the cooling rate of the furnace. The evaluation of the sintered pieces brought the following results:

PorosityA-1, through and through Thickness of the zone enriched with cobalt is approximately 14.8 µm Thickness of the zone depleted of solid solution up to 19.7 µm Medium Rockwell "A" hardness in the body of the body 92.4 Magnetic saturation 130 Gauss · cm³ / g Co Coercive force (Hc) 230 Oersted

Example 11

A further 5000 g were from the original, according to Example 9 prepared separated. Pre-ground TiCN in an amount of 95.4 g (1.9% by weight) was added, Mixed, sieved, dried and dried for 16 hours placed in the hammer mill as described in Example 9. Test pieces were then pressed and at 1496 ° C with the Test pieces sintered according to Example 10.

The evaluation of the sintered pieces brought the following Results:  

Porosity A1, rich in eta phase, through and through Thickness of the zone enriched with cobalt is approximately 12.5 µm The thickness of the zone depleted in solid solution is up to 16.4 µm Medium Rockwell "A" hardness in the body 92.7 Magnetic saturation 120 Gauss-cm³ / g Co Coercive force, Hc260 Oersted

Example 12

The following mixture was made using the following described two-stage grinding process:

Level I

The following fabrics were made with 17.3 kg of 4.8 mm large WC-Co cycloids in a WC-Co lined Grinding container with an inside diameter of Given 181 mm and a length of 194 mm. The grinding bowl was around its cylinder axis with 85 revolutions per Rotates for 48 hours (244,800 revolutions):

455 g (6.5% by weight) Ni 280 g (4.0% by weight) TaN 112 g (1.6% by weight) TiN 266 g (3.8% by weight) NbN 42, 7 g (0.6 wt%) carbon 14.0 g surfactant (Ethomeen S-15)
1500 ml perchlorethylene

Stage II

The following substances were then added to the grinding container and rotated for a further 16 hours (81,600 revolutions):
5890 g (83.6% by weight) WC 105 g paraffin (Sunoco 3420)
1000 ml perchlorethylene

This mixture was balanced so that a binding alloy with 10 wt .-% W and 90 wt .-% Ni. To the mixture was removed from the grinding container sifted wet through a 400 mesh sieve (Tyler) Dried at 93 ° C under a nitrogen atmosphere and in given a 40 mesh sieve hammer mill.

The samples were pressed into tablets, at 1450 ° C. 30 Minutes under a nitrogen atmosphere and one Pressure of 6.9 × 10³ Pa sintered and then with the im Oven cooled down cooling rate. After sintering, the samples were hot isostatically pressed (HIPed) for 60 minutes at 1370 ° C in a helium atmosphere at a pressure of 1 × 10⁸ Pa. The optical-metallographic examination of the hot isostatic pressed samples gave a porosity of the type A-3, through and through, and a thickness of the solid solution depleted zone of about 25.8 µm.

The pattern was then produced again and examined using the energy dispersive x-ray line scan analysis (EDX) at different distances from the cutting breast. Figure 3 shows a graphical representation of the change in relative nickel, tungsten, titanium and tantalum concentrations as a function of the distance from the cutting face of the pattern. It can clearly be seen that there is a layer near the surface in which titanium and tantalum, which form carbides present in solid solution with tungsten carbide, are at least partially depleted. This zone, depleted of solid solution, extends approximately 70 µm towards the inside. The discrepancy between this value and the value reported above is attributed to the fact that the pattern was re-created between the two evaluations, so that different levels within the pattern were examined in the examination.

With the depletion of titanium and tantalum is accompanied by a layer enriched with nickel (see Fig. 3). The nickel concentration in the enriched layer decreases from 30 to 10 µm as the distance from the cutting face decreases. This shows that the nickel in this zone was partially volatilized during vacuum sintering.

The peak of the titanium and tantalum concentration at 110 µm is on the scanning of a randomly large grain or large grains returned, which is a high concentration have on these elements.

The two parallel, horizontal lines show the typical scatter that occurs when analyzing the main part of the pattern is obtained to the nominal values of the chemical Properties of the mixture.

Example 13

The following mixture was made using the following described two-stage grinding process used:

Level I

The following fabrics were made according to Stage I of Example 12 grind together:

Example 12:

455 g (6.4% by weight) Ni 280 g (3.9% by weight) TaH 112 g (1.6% by weight) TiN 266 g (3.7% by weight) NbN 61, 6 g (0.9% by weight) C Ravin 410, 502 14 g surfactant (Ethomeen S-15)
2500 ml perchlorethylene

Stage II

After that, the following substances were put in the grinding container given and rotated for another 16 hours:

5980 g (83.6% by weight) WC 140 g paraffin (Sunoco 3420)

The composition of this mixture was chosen so that a binding alloy with 10 wt .-% W and 90 wt .-% Ni originated.

After the mixture had been taken out, it was sieved and dried and ground in a hammer mill, according to Example 12.

Pressed specimens were held at 1466 ° C for 30 minutes vacuum sintered under an atmosphere of 35 microns. The sintered samples had an A-3 porosity, through and through, and up to 13.1 µm thick, more solid Solution impoverished zone.

Example 14

A mixture was two-step using the following Grinding process:

Level I

The following fabrics were made with 17.3 kg of 4.8 mm large WC-Co cycloids in a WC-Co lined Grinding container with an inside diameter of Given 190 mm and a length of 194 mm. The grinding bowl was around its axis at 85 revolutions per minute Rotated for 48 hours (244,800 revolutions):

177 g (2.5% by weight) HfH₂ 182.3 g (2.5% by weight) TiH₂ 55.3 g (0.8% by weight) carbon 459 g (6.4% by weight ) Co 14 g surfactant (Ethomeen S-15)
2500 ml perchlorethylene

Stage II

The following substances were then placed in the grinding container and rotates another 16 hours (81 600 revolutions):

6328 g (87.9% by weight) WC 140 g paraffin (Sunoco 3420)

The composition of this mixture was chosen so that a binding alloy with 10 wt .-% W and 90 wt .-% Co originated.

After the mixture was removed from the grinding container sifted through 400 meshes moist, at 93 ° C under one Nitrogen atmosphere dried and in a hammer mill ground through a 40 mesh sieve.

Insert blanks were pressed and then at 1468 ° C Sintered for 30 minutes under a vacuum of 35 microns, with most of the hydrogen in the sample pieces evaporated. During the sintering the pieces are placed on an NbC powder release agent.

The sintered pattern had in the enriched zone a porosity of type A-2 and in the non-enriched The main part is a porosity of type A-4. The pattern had an average Rockwell "A" hardness of 90.0; one more solid Solution depleted zone with a thickness of 9.8 µm; and a Coercive force, Hc, from 150 Oersted.

Example 15

A material mixture of that described in Example 9 Mixture corresponding composition was mixed, ground and pressed into blanks of inserts. The Blanks were then sintered, ground, heat treated and sanded again (only the flanks), in exact agreement with the method according to Example 9. In the heat treatment carried out at the end  however, a cooling rate of 69 ° C / h applied.

An insert was analyzed by EDX line analysis at various distances from the insert's cutting breasts. The results of this analysis are shown by the graph in FIG. 2. It shows the existence of a layer enriched with cobalt, which extends from the cutting breasts into the interior at a depth of approximately 25 µm and which is followed by a layer of material partially depleted in cobalt, which is approximately 90 µm from the cutting breasts in the inside extends into it. Although not shown in FIG. 2, partial depletion of solid solution was found in the cobalt-enriched layer, while enrichment of solid solution was found in the partially cobalt-depleted layer.

The two horizontal lines show the typical scatter the nominal values of the chemical properties of the mixture, which occurs when analyzing the material of the main part.

Claims (13)

1. Sintered hard metal body with a porosity of type A to B, with a layer enriched with binder, depleted in solid solution carbides ( 14 ) near its surface, with a depleted in binder, enriched with solid carbides below the further layer ( 16 ) with a layer ( 14 ) enriched with binder and optionally with a hard, dense, high-melting, firmly adhering coating ( 10 ),
available through

• - Making a powder mixture
  • a) tungsten carbide as the main component,
  • b) at least 3% by weight of a binder consisting of Co, Ni, Fe or one of the alloys of these metals and
  • c) 0.5 to 2% by weight, based on the mass of the powder mixture, of Ti, Zr, Hf, V, Nb and / or Ta in the form of their metals, alloys, hydrides, nitrides or carbonitrides,
• Pressing this powder mixture into a compact,
• - Sintering the compact at a temperature above the melting point of the binder
• - and optionally applying the high-melting coating.

2. hard metal body according to claim 1, characterized in that the chemical agent titanium nitride or Is titanium carbonitride. 3. hard metal body according to claim 1 or 2, characterized by a binder content of between 5 and 10% by weight.   4. hard metal body according to one of claims 1 to 3, characterized by a total content of cubic Carbide of at most 20% by weight. 5. Hard metal body according to one of claims 1 to 4, characterized in that the layer enriched with binder ( 14 ) has on the outer surface a metal content of 1.5 to 3 times the average metal content of the body. 6. Hard metal body according to one of claims 1 to 5, characterized in that the layer enriched with binder ( 14 ) extends from the outer surface of the body in the direction of the interior to a minimum depth of 6 microns. 7. Hard metal body according to one of claims 1 to 6, characterized in that the binder-enriched layer ( 14 ) extends from the outer surface of the body towards the inside to a depth of 12 to 50 microns. 8. Carbide body according to one of claims 1 to 7, characterized in that the coating ( 10 ) from one or more layers of the carbides, nitrides, borides or carbonitrides of titanium, zirconium, hafnium, niobium, tantalum or vanadium or from the oxide or oxynitride of aluminum. 9. hard metal body according to claim 8, characterized in that the coating ( 10 ) contains a layer of titanium carbide and a layer of titanium nitride and that the total thickness of the coating ( 10 ) is less than about 10 microns. 10. A method for producing the hard metal body according to one of claims 1 to 9 by producing a powder mixture of the desired composition, pressing this mixture, sintering the compact and optionally applying a high-melting coating, characterized in that the powder mixture

• a) tungsten carbide as the main component,
• b) at least 3% by weight of a binder consisting of Co, Ni, Fe or one of the alloys of these metals and
• c) up to 15% by weight of an effective amount of Ti, Zr, Hf, V, Nb and / or Ta in the form of their metals, alloys, hydrides, nitrides or carbonitrides to form the layer ( 14 ) enriched with binder

produced and the compact formed from the powder mixture at 1285 to 1540 ° C for at least 15 minutes is vacuum sintered. 11. The method according to claim 10, characterized in that the compact at 1370 to 30 to 150 minutes 1500 ° C is sintered. 12. The method according to claim 10 or 11, characterized in that the compact at a pressure of between 0.133 and 0.200 hPa is sintered.